2 MODES OF SURVIVAL OF FISSION YEAST WITHOUT TELOMERASE

Deletion of the telomerase catalytic subunit gene trt1(+) in Schizosac charomyces pombe results in death for the majority of cells, but a sub population survives. Here it is shown that most survivors have circula rized all of their chromosomes, whereas a smaller number maintain thei r telomeres presumably through recombination. When the telomeric DNA-b inding gene taz1(+) is also deleted, trt1(-) taz1(-) survivors use the recombinational mode more frequently. Moreover, the massive elongatio n of telomeres in taz1(-) cells is absent in the double mutant. Thus, Taz1p appears to regulate telomeric recombination as well as telomeras e activity in fission yeast.